WO2007056240A2

WO2007056240A2 - Apparatus and method for the conversion of thermal energy sources including solar energy

Info

Publication number: WO2007056240A2
Application number: PCT/US2006/043123
Authority: WO
Inventors: Michael D. Strathman
Original assignee: Mev Technology, Inc.
Priority date: 2005-11-08
Filing date: 2006-11-04
Publication date: 2007-05-18
Also published as: WO2007056240A3; US20070101989A1

Abstract

Systems and methods to efficiently utilize thermal energy such as solar energy, geothermal energy, waste-heat energy, bio-mass combustion energy, or other equivalent forms of energy, convert the thermal energy (120) to another useful form of energy, such as electricity or mechanical work using a thermodynamic cycle in which a working fluid medium (126) may be expanded in a constant pressure environment (130) to move a storage medium (129) comprising another fluid, slurry or mass to a higher potential energy level (110), from which the storage medium may be released through a generator (1 12) or the like to produce another form of energy.

Description

Apparatus and Method for the Conversion of Thermal Energy Sources Including Solar Energy

TECHNICAL FIELD

[0001] The invention relates generally to energy conversion systems and methods, and more particularly to the conversion of solar and similar forms of heat energy to other forms of energy.

BACKGROUND

[0002] There are several sources of relatively abundant, relatively inexpensive low density thermal energy, such as solar energy, geothermal energy, waste-heat energy, and equivalent types of low energy density heat energy. Conversion of this thermal energy to other forms of more useful energy, while desirable to meet today's increasing energy demands and costs and because of environmental reasons, has not been widely used because it has been relatively expensive and inefficient. Solar energy has a relatively low power density, typically providing an average of 4-6 kilowatts per square meter per day for a given flat surface collector area in the continental USA, and conventional approaches to increase energy production have focused on the use of very large arrays of mirrors or lens systems to concentrate the photon energy of solar radiation, which are problematic.

[0003] The problems with very large arrays include the installation and land cost, vulnerability to high winds, dust and sand damage to mirrors and lenses, and the traditional maintenance costs for both tracking systems and the lens/mirror systems. Mirror and/or lens systems are also susceptible to degradation over time, and the tracking equipment to keep the mirror and/or lens properly positioned in correspondence with the movement of the sun is complex and costly to maintain.

[0004] Conventional generation of electricity from solar energy, has also had several serious problems. One common method to generate electricity from solar energy is the use of photovoltaic cells ("PV"). However, conventional PV systems typically use less than 30% of the solar light frequency spectrum, that is photons having a wavelength above that needed to create hole-electron pairs in a PV cell. Therefore only a fraction of the total solar energy is converted to electricity, and the efficiency of converting solar energy into usable power from photovoltaic cells is fairly low, requiring either very large surface areas or solar energy concentrators. The photovoltaic cells also degrade over time and lose most of their DC electricity production efficiency, typically there is a significant decrease in output after 20 years or less. Since most electrical power is AC, inverters are required to convert the DC electricity from the photovoltaic cells to AC electricity, and these electrical inverters have relatively short mean times between failures, typically requiring repair within five years or less. In a current study of energy usage in California, for example, only about 0.5% of the useable energy comes from solar energy, as the cost of a solar PV KWH of electricity is on the order of 10 times greater than that from fossil fuel.

[0005] An alternative to photovoltaic systems is to utilize thermally powered heat engines operating on various thermodynamic cycles (e.g., an organic Rankine or other similar cycle). Thermally powered engines can generally use fluids to both absorb the heat from a heat source (e.g., solar energy, geothermal energy, waste-heat energy, bio-mass combustion, and other such types of energy) to create a gas, and use high pressure gas to drive some sort of mechanical device or expander. The fluids can be a single fluid, or a mixture of two or more fluids such as a binary solution of ammonia and water, or the like. However, such systems have not been found to be cost effective for large scale use. Because of the generally low temperature differential between the hot side of an engine and a condenser, conventional thermal power engines suffer from low efficiency in energy conversion, expensive equipment and materials, unreliability for long-term operation, and costly maintenance.

[0006] There are three main types of passive thermal energy collector systems used for collecting thermal energy (e.g., solar energy, or an equivalent). Low-temperature collectors (unglazed) normally operate at up to approximately 18 F° (10 C°) above ambient temperature, and are most often used for heating swimming pools. Often, the pool water is colder than the air, and insulating the collector would be counter-productive. Low-temperature collectors are typically extruded from polypropylene or other polymers with UV stabilizers. Flow passages for the pool water are molded directly into the absorber plate, and pool water is circulated through the collectors with the pool filter circulation pump. Swimming pool heaters typically cost from $10 to $40/ft² (based on 2004 prices).

[0007] Mid-temperature collectors are usually flat plates insulated by a low- iron cover glass and fiberglass or poly-isocyanurate insulation. Reflection and absorption of sunlight in the cover glass reduces the efficiency at low temperature differences, but the glass is required to retain heat at higher temperatures. A copper absorber plate with copper tubes welded to the fins is typically used. In order to reduce radiant losses from the collector, the absorber plate is often treated with a black nickel selective surface, which has a relatively high absorptivity in the short-wave solar spectrum, but a relatively low-emissivity in the long-wave thermal spectrum. Mid-temperature collectors typically range in cost from $90 to $120/ft² of collector area (based on 2004 prices).

[0008] High-temperature collectors utilize evacuated tubes around a receiver tube to provide high levels of insulation and often use focusing curved mirrors to concentrate sunlight. High temperature collectors are normally used for absorption cooling or electricity generation, but are also sometimes used for mid-temperature applications, such as commercial or institutional water heating as well. Evacuated tube collectors themselves typically cost about $75/ft², but use of curved mirrors and economies of scale get this cost down for large system sizes to a relatively low cost of $40-70/ft² of collector area (based on 2004 prices).

[0015] A need exists for a higher efficiency, lower cost systems for thermal energy conversion and utilization, in general, and especially for the utilization of solar energy that avoid the foregoing and other problems of known approaches. There is a need for systems that do not require expensive equipment, materials, or maintenance, are relatively stable and non- degradable in long-term operation, and have good efficiency. It is to these ends that the present invention is directed.

SUMMARY OF THE INVENTION

[0016] The invention affords a system and method which use the phase transformation of a working expansion medium (e.g., a liquid, or a solid such as dry ice) into a gas during heat absorption. During expansion, the enthalpy of the system is the physical work done plus the work of the latent heat of fusion which is used to change the liquid to a gas. This increases the internal energy of the system, which may be recovered during a cooling period, such as night time, when the gas is cooled and returned to the liquid state and the heat evolved is emitted into deep space on the dark side of the planet which is not facing the sun. This cycle creates a change in the solar cross section of the planet, as all energy that is captured by phase transformation from liquid to gas over a given absorption area is released into space by black body radiation during the night time operations. Energy systems in accordance with the invention, if utilized on a large scale, can efficiently produce energy such as electricity or other forms of useful power and power storage, as well as help to reduce global warming.

[0017] Advantageously, the invention may provide a heat energy conversion system that is coupled to the normal varying, more or less sinusoidal, energy field that characterizes the daily solar heat cycle due to the daytime exposure to the sun and the subsequent nighttime exposure to a cold heat sink (e.g., deep space). This cycle comprises a heat energy source (or photons which can be converted to heat) and an energy sink. The^' energy source may be the sun (in the case of the planet earth) and the energy sink may comprise interstellar space (deep space on the side of the earth not facing the sun). A portion of heat energy absorbed during daylight may go directly into generating external work via a prime mover, and the rest of the absorbed heat may be used to raise the enthalpy (or internal energy) of the system. The energy that goes into driving an expansion medium, i.e., a working fluid or working liquid, to the gas phase raises the internal energy of the system. This energy can be stored in the system and can be emitted via black body radiation to deep space on during nighttime operations. Heat is not absorbed by the system, rather it passes through the system, is absorbed in the liquid-to-gas phase transformation, and then is emitted in the transformation of the expansion medium from gas to liquid.

[0018] The invention may utilize, in part, the fact that when an expansion fluid makes the transformation from a liquid to a gas, the volume occupied by the expansion fluid may increase by several, typically about three, orders of magnitude (1000 times larger). The liquid-to-gas transformation is done with the liquid at a high pressure, as will be shown later on the pressure vapor curve for the expansion fluid. Heat is supplied by the sun to drive the temperature of the expansion fluid to the boiling point and then into the liquid- to-gas transformation. As the volume of gas increases, this volume change can be used to displace another working medium, referred to as a storage medium, to a higher potential energy. Once the storage medium is at the higher potential energy it can either be used directly being returned to a- lower potential through a prime mover which extracts energy from the storage medium, or it can be stored at the higher potential energy level for use at some later time.

[0019] The invention can be used to pump a working medium, such as water, to a higher potential energy and transport it over a hill such as the California aqueduct passing over the Grapevine area of California, where it can be available for different uses. In this case the working medium (water) can be replaced on the pumping side by water flowing in the California aqueduct from Northern California to Southern California

[0020] The invention also affords a pixelized collection system to allow for more efficient use of the absorbed heat energy, and enables use of cells that have been fully expunged of the working medium by the gaseous expansion medium to heat the liquid expansion medium for subsequent cells in the pixelization collector, thus increasing the overall efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 illustrates a block diagram of a conventional Rankine cycle engine, as used in conventional solar energy applications;

[0022] FIG. 2 illustrates a block diagram of a modified Rankine cycle in accordance with one embodiment of the invention;

[0023] FIG. 3 illustrates a vapor pressure curve of an expansion medium, such as ammonia, that may be used in the invention;

[0024] FIG. 4 is a block diagram of a thermal energy system in accordance with a first embodiment of the invention;

[0025] FIG. 5 is a more detailed block diagram of the system shown in FIG. 4;

[0026] FIG. 6 is a diagrammatic view of an implementation of a thermal energy system in accordance with the invention;

[0027] FIG. 6A is a diagrammatic view of a thermal energy system in accordance with an alternative embodiment of the invention where energy production is only required during day light hours and high potential energy storage is not used;

[0028] FIG. 7 is a flowchart of a method in accordance with the embodiment of FIGs. 4-6, 6A for converting thermal energy to another useful form of energy;

[0029] FIG. 8 is a flowchart of another method in accordance with the invention for converting thermal energy to another form of energy in a pixilation system of the type illustrated in FIGs. 15A-C ;

[0030] FIG. 9 illustrates a flowchart of a method of generating energy, in accordance with another embodiment of the invention;

[0031] FIG. 10 illustrates a flowchart of a method of generating electricity, in accordance with a further embodiment of the invention;

[0032] FIG. 11 is a diagrammatic view of the solar energy generation system shown in FIG. 6; [0033] FIG. 12 is a diagrammatic view of a solar pumping system in accordance with the invention;

[0034] FIG. 13 is a cross-sectional view of a containment assembly that may be used in the systems of the invention;

[0035] FIG. 14 is a diagrammatic view of another embodiment of a containment assembly, partially broken away, that may be used in the systems of the invention;

[0036] FIG. 15A is a block diagram of a pixelized energy collection system in accordance with another embodiment of the invention.

[0037] FIG. 15B is a more detailed diagrammatic view of a pixelized energy generation system in accordance with another embodiment of the invention having two or more interconnected energy generator assemblies;

[0038] FIG. 15C illustrates a diagrammatic view of an alternative embodiment of the system of FIG. 15B;

[0039] FiG. 16 is a flowchart of a method of converting thermal energy to another useful form of energy from a plurality of interconnected energy generator assemblies; and

[0040] FIG. 17 illustrates a fractal solar energy collector array that may be employed for the pixelized collection of energy in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Embodiments of the invention can be constructed from commercially available components. In all of the embodiments disclosed below, various different materials may be used for the chambers, reservoirs, and piping, including but not limited to various plastics, rubbers, resins, ceramics, cements, and metals, or other equivalent man-made materials. The collector may be a low-temperature collector, a mid-temperature collector, a high- temperature collector, or a combination of different types of collectors.

[0042] The invention employs a working medium, also referred to as an expansion medium, and a storage medium. The expansion medium and storage medium of the invention preferably comprise fluids, as will be explained. These two fluids may be the same, or one fluid may be used as the expansion medium and a second different fluid may be used as the storage medium. Materials that may be utilized for the working (expansion) fluid and storage fluid include, but are not limited to, acetone, alcohol, water, various water solutions, ammonia and water solutions (e.g., such as an 80% ammonia and 20% water solution, or equivalents), liquefied natural gas (LNG), chloro- fluorocarbon (CFC) refrigerants (e.g., R-410A, R-22, R-32, R-125, R-407C, R- 134A), the equivalent hydrogenated CFC (HCFC) refrigerants, ammonia, carbon dioxide, or other non-aqueous fluids having similar vapor pressure curves. Preferred criteria for selecting the expansion and storage^' media will be explained in connection with FIG. 3. Additionally, as will also be explained, the storage medium may also comprise a slurry, a powder, or a solid mass that can be transformed to a higher potential energy.

[0043] The invention affords a system for generating useful mechanical power, for generating chemical energy or for supplying chemical fuels (e.g. chemical fuels generated from electrolysis, e.g., hydrogen and oxygen, or equivalents), or connected to one or more electrical generators for producing either AC or DC electricity. The invention may also be used to generate cryogenic fluids such as liquid nitrogen. Some embodiments of the invention can accommodate variations in the heights available for utilizing a storage medium, if necessary.

[0044] The invention has some similarities to a Rankine cycle engine and to a Sterling engine, but differs in several significant ways. First, the invention may utilize a substantially constant pressure and a changing volume of a working medium, e.g., a fluid, the volume increasing during an expansion phase and decreasing during a contraction phase, to produce useful work. Work may be extracted by a corresponding increase in the volume of a displacement chamber, for example, caused by the conversion of a liquid expansion medium to a gas. This expansion ratio of gas to liquid may be on the order of 1000 times the volume in the gas phase verses the liquid phase. [0045] FIG. 1 illustrates a block diagram of a conventional Rankine cycle engine. As shown, there is a boiler 102 connected with a pipe 169 to a turbine 112, which is connected with an output pipe 167 to a condenser 124. The condenser is connected with an output pipe 165 to a feed pump 106 that supplies boiler 102 by an output pipe 104. The expansion medium in a conventional Rankine cycle engine is typically water.

[0046] The turbine 112 (e.g., a steam turbine, water turbine, or generator) utilizes a substantially isentropic expansion; the condenser 124 utilizes a substantially isobaric heat rejection; the feed pump 106 utilizes a substantially isentropic compression; and the boiler 102 utilizes a substantially isobaric heat supply. Heat 103 is supplied to the boiler 102 and heat 105 is rejected by the condenser 124. The work output 107 is from the turbine and the work input 108 is to the feed pump 106. The net work produced by this engine is the difference of the work output 107 and the work input 108.

[0047] In a conventional Rankine cycle engine, work is extracted by expanding a high pressure gas (and volume) and reducing the gas pressure during this expansion cycle. Unlike a Rankine cycle, as will be explained, the invention does not have to expand the gas to a lower pressure to extract work. It may reduce the gas temperature and volume, and heat a liquid expansion medium to near its boiling point. The expansion of the gas may be used to displace a storage medium from a low potential energy ("LE") to a high potential energy ("HE"). As the storage medium is returned to the lower potential energy, it may pass through a prime mover (e.g., a turbine, generator, pump, mechanical power take off) or other system that uses the energy change to produce work. Thus, while the work extracted is from the expansion of the working medium from liquid to gas, the invention does not expand the gas to a lower pressure as is done in a conventional Rankine cycle.

[0048] In addition, as mentioned above, the invention may utilize the fact that work is required for the. transformation of a liquid to a gas, (the latent heat of fusion or internal energy of the system), and physical work may be extracted as the liquid expands, typically about 1000 times, as it goes through the phase transformation at a high pressure. This expansion of volume may be used to generate physical work, as in a collector/expansion system. If the collector/expansion system is composed of a plurality of small chambers, then when a given chamber has all of its storage medium (the "storage^" medium" may be a fluid such as water, a slurry or powder, or a physical mass that can be lifted to a higher potential energy) displaced by the expansion medium, that chamber can be isolated from the main system's storage media, and the heat trapped in that smaller chamber can be used to raise an expansion fluid temperature to just below the liquid-to-gas transformation temperature. The invention may employ several fully displaced chambers so that all of the heat energy that was used to raise the first chamber liquid to the boiling point can be recovered from the hot working medium gas.

[0049] As the temperature of the gas is lowered, the chamber can then be partially refilled with the storage media and then reheated to force more storage media to a higher potential. This is similar to the reheat cycle in an advanced reheat Rankine cycle engine or somewhat like that of a Sterling engine.

[0050] Thus, the invention differs substantially from a conventional Rankine cycle in the fact that the gas that is evolved from the expansion medium is not expanded in an increased volume and the temperature is not lowered. Rather, the pressure can be retained at a constant value and the volume may be expanded to contain the increased gas volume due to the liquid-to-gas transformation of the expansion media. The increased volume may be used to move the working medium to a higher potential energy, from which it may be run through a prime mover (turbine, expander, pressurizer, etc. ) to produce work as it moves to a lower potential energy. The working medium may then be returned to its lowest potential energy as it is used to pressurize the gaseous expansion medium and help (with cooling) to drive the phase transformation of the expansion media from the gas phase to the liquid phase. The invention may comprise a binary system that includes an expansion medium which is separate from the working media, and the expansion medium drives the working media to a higher potential energy. In addition the invention does not require a conventional feed water pump as does a conventional Rankine cycle engine.

[0051] FIG. 2 illustrates a block diagram of a thermodynamic cycle of a modified Rankine cycle engine in accordance with the invention. Referring to FIG. 2 there is a reservoir 110, connected with an output pipe 169, to a turbine (e.g., steam turbine, water turbine, generator, or equivalent) 112 with an output pipe 167 witch is connected to a condenser 124, connected with an output pipe 165 to the containment assembly 130, may be connected by a pipe 163 to the reservoir 110. There is no feed pump 106 and no output pipe 104, as in a conventional Rankine cycle engine. Heat 103 may be supplied to the containment assembly 130, and heat 105 is rejected by the condenser 124. The work output 107 from this engine is from the prime mover 112.

[0052] The prime mover 112 (e.g., a steam turbine, water turbine, generator, or equivalent) may utilize a substantially isentropic process, the condenser 124 may utilize a substantially isobaric heat rejection, and the reservoir 110 in one embodiment may be filled with a storage medium (not shown) moved by pressure provided by an expansion medium (not shown). Several possible materials could be utilized for the expansion medium and storage medium, including acetone, alcohol, water, various water solutions, ammonia and water solutions (e.g., such as an 80% ammonia and 20% water solution, or equivalents), liquefied natural gas (LNG), chloro-fluorocarbon (CFC) refrigerants (e.g., R-410A, R-22, R-32, R-125, R-407C, R-134A), the equivalent HCFC refrigerants, ammonia, carbon dioxide, or other non-aqueous fluids having substantially similar vapor pressure curves. Substantially the same fluid may be used for both the expansion medium and the storage medium. The expansion medium in the modified Rankine cycle engine can be any fluid having a suitable vapor pressure curve, for example, as shown in FIG. 3 (and described below).

[0053] FIG. 3 illustrates a vapor pressure curve of an exemplary expansion medium, ammonia, that may be used in the invention. The vertical axis 302 indicates the vapor pressure of the expansion medium, and the vapor pressure curve 304 of the expansion medium is shown plotted, between the vertical axis 302 and the horizontal axis 306 indicating the temperature in degrees Kelvin and the horizontal axis 308 indicating the temperature in degrees Celsius.

[0054] Suitable expansion medium for the invention is preferably selected to have a high pressure at the high temperature side of the thermodynamic cycle, and a fairly low pressure in the condensation side of the cycle. Two suitable fluids are ammonia and carbon dioxide which have pressures of about 40-50 bar at a working temperature of about 30-40⁰C above ambient, and also have a good pressure, on the order of 10 bar, for the condensation of gas back to liquid. Also important is the latent heat of fusion vs. the expansion factor. CO₂ may have a slight advantage in efficiency as compared to ammonia in this regard.

[0055] The process of evaporation in a closed chamber will proceed until there are as many molecules returning to the liquid as there are escaping. At this point the vapor is said to be saturated, and the pressure of that vapor is called the saturated vapor pressure. Since the molecular kinetic energy is greater at higher temperature, more molecules can escape the surface and the saturated vapor pressure is correspondingly higher. If the liquid is open to the air, then the vapor pressure is seen as a partial pressure along with the other constituents of the air. The temperature at which the vapor pressure is equal to the atmospheric pressure is called the boiling point. The phase change of a fluid from a liquid to a vapor (and the reverse process) can be utilized in multiple ways by the invention, as described below.

[0057] FIG. 4 illustrates a block diagram of a system in accordance with a first embodiment of the invention to utilize thermal energy. The system includes a high potential energy reservoir 110, a turbine 112, a low potential energy reservoir 114, and a containment assembly 130 containing the storage media 129. The system also includes a thermal energy collector 120 connected to an expansion medium reservoir 126, which receives the expansion medium 127 from a condenser 124, which is connected to the containment assembly 130. The expansion medium 127 is capable of undergoing a phase change from a liquid to a vapor upon the application of thermal energy, and disposed to circulate through the thermal energy collector 120, the containment assembly 130 and the condenser 124. The storage media 129 circulates through the high potential energy reservoir 110, the turbine 112, the low potential energy reservoir 114, and the containment assembly 130 as a result of displacement in the containment assembly 130 caused by the vaporization of the expansion medium 129. The thermal energy collector 120 can collect heat from one or more sources (e.g., solar energy, geothermal energy, waste-heat energy, bio-mass combustion, and other equivalent types of energy).

[0058] FIG. 5 illustrates in more detail the system shown in FIG. 4. FlG. 5 shows, for example, more details of the containment assembly, and includes a plurality of valves that may be used to control the system. As shown, containment assembly 130 may have a containment assembly interior 116 containing the storage medium (fluid) 129, and a displacement chamber 122 containing the working vapor 128.

[0059] Valve 143 may control the flow in the pipe between the high potential energy reservoir 110 and the containment assembly interior 116 in the containment assembly 130. Valve 142 may control the flow in the pipe between the low potential energy reservoir 114 and the containment assembly interior 116 in the containment assembly 130. Valve 149 may control the flow in the pipe between the low potential energy reservoir 114 and the containment assembly interior 116 in the containment assembly 130. Valve 141 may control the flow in the pipe between the turbine 1 12 and the low potential energy reservoir 114. Valves 146 and 148 may control the flow of expansion medium (working fluid) 127 between the thermal energy collector 120 and the expansion medium (working fluid) reservoir 126. Valve 147 may control the flow of working fluid 127 between the condenser 124 and the working fluid reservoir 126; and valve 145 may control the flow of working fluid vapor 128 between the condenser 124 and the displacement chamber 122 in the containment assembly 130.

[0060] FIG. 6 illustrates diagrammatically an implementation of the system of FIGs. 4 and 5 in accordance with a preferred embodiment of the invention. As will be described, the invention may be implemented as a solar energy system using natural or man-made geographical features, such as lakes, as reservoirs. FIG. 6 illustrates lakes as reservoirs. However, it may be appreciated that the reservoirs may take other forms, and that the invention may be implemented in other contexts.

[0061] As shown in FIG. 6, the system may include a high potential energy reservoir 110 (such as lake 1), a turbine 112, a low potential energy reservoir 114 (lake 2), and a containment assembly 130 (pump chamber) containing the storage medium 129 (e.g., water) in the containment assembly interior 116. The system also includes a thermal energy collector 120 (e.g., an evaporator) connected to an expansion medium reservoir 126 (fluid tank), which receives expansion medium 127 from a condenser 124, which is connected to the containment assembly 130. The expansion medium, preferably a fluid, is capable of undergoing a phase change from a liquid to a vapor 128 (gas) in displacement chamber 122 upon the application of thermal energy (e.g., from the sun 600) and disposed to circulate through the thermal energy collector 120, the containment assembly 130 and the condenser 124. The storage medium (water) 129 circulates through the high potential energy reservoir 110, the turbine or prime mover 112, the low potential energy reservoir 114, and the containment assembly 130 as a result of displacement caused by the vaporization of the expansion medium 129 in the displacement chamber 122. Valves v1 , v2, v3, v4, v5, v6, v7, and v8, which are analogous to various ones of the valves shown in FIG. 5, control the system and will be described in detail in connection with FIGs. 11 and 12. The sun may be the thermal energy source in this embodiment, but in other embodiments other heat sources may be used alone or in combination to supply the thermal energy.

[0062] Generating electrical energy in large quantities for an electrical power grid is not trivial, especially for AC electricity power grids. Large amounts of electricity needed by an electrical power grid cannot be stored as electricity in conventional systems, although it may be stored in another form. Therefore, the energy taken from an electrical power supply grid must always be equal to the energy being delivered by the electrical power plants. If this were not the case, the frequency and voltage of the supply grid would deviate from standard values.

[0063] Pumped storage plants address this problem by storing electrical energy as potential energy. They pump water to an upper reservoir at times of surplus energy on an electrical supply grid-typically, at night. This potential energy is then released through a hydro-electrical generator at times of high demand. Use of hydroelectric turbines allows direct energy conversion to AC electrical power. Electrical DC to AC conversion (used in many conventional solar energy systems) is not required, thereby significantly reducing the complexity, reliability problems, and cost of construction and maintenance, as compared to conventional DC electricity supply systems.

[0064] FIG. 6A illustrates a modification of the system of FIG. 6 which is used for power generation during daylight operations only. In this system, the flow of the working medium (water) is not supplied to a high potential energy reservoir, such as lake 1 , but is directly input into the inlet of the prime mover or turbine 112 to generate power, such as electricity.

[0065] FIG. 7 is a flowchart of a method of converting thermal energy to another useful form of energy, in accordance with the embodiment of the invention shown in FIGs 4-5. Referring to FIG 7, the method begins at 702. At 704, thermal energy is absorbed into an expansion medium, such as a working fluid. At 706, at least a portion of the expansion medium is vaporized to exert pressure on a storage medium, such as a storage fluid, to displace at least a portion of the storage fluid from a lower potential energy state to a higher potential energy state. This corresponds, for example, to transporting the storage fluid from chamber 116 of containment assembly 130 of the system of FIG. 6 to the reservoir 110. At 708, the portion of the expansion fluid that was vaporized is substantially condensed, corresponding, for example, to condensing a portion of the expansion gas 128 from chamber 122 back to a liquid in condenser 124. At 710, a portion of the storage fluid displaced to a higher potential energy state (to reservoir 110, FIG. 6) is supplied to at least one turbine to produce a second form of energy. At 712, substantially the portion of storage fluid from the at least one turbine is supplied to at least one lower potential energy state. The method ends at operation 714.

[0067] FIG. 8 illustrates a flowchart of another method in accordance with the invention for converting thermal energy to another form of energy in a pixelized system (such as will be described in more detail in connection with FIGs 15A-C) which combines the contributions of multiple energy collector/generator assemblies. The method contemplates a system that uses of one or more expansion and storage media, e.g., fluids, as well as multiple separate components for some system components, such as thermal energy collectors, containment assemblies, condensers, prime movers, etc. The method begins in operation 802. At 804, at least one expansion medium (working fluid) is stored in a working fluid reservoir. At 806, the at least one working fluid is communicated to at least one thermal energy collector to vaporize a portion of the at least one working fluid. At 808, the vaporized portion of at least one working fluid is communicated into at least one containment assembly, where the portion of the vaporized working fluid exerts pressure on at least one storage medium (fluid) in the at least one containment assembly to transport the at least one storage fluid to at least one higher potential energy reservoir. At 810, the portion of vaporized at least one expansion fluid from the at least one containment assembly is communicated to at least one condenser, where the vaporized portion of the expansion fluid is condensed and communicated to at least one expansion medium reservoir. At 812, at least one storage fluid from the least one higher potential energy reservoir is communicated to at least one turbine generator, where another form of energy, e.g., electricity, is generated, and at 814 the at least one storage fluid is communicated from the at least one generator to at least one lower potential βnergy reservoir. At 816, the at least one storage media is communicated from the at least one lower potential energy reservoir to the at least one containment assembly, and the method ends at 818.

[0068] FIG. 9 is a flowchart of a method of generating energy that is somewhat similar to that shown in FIG. 7, except that the method is more precisely focused on FIG. 6. The method begins at 902. At 904, at least one expansion medium (working fluid) is stored in an expansion medium reservoir. At 906, the at least one working fluid is communicated to an energy collector. At 908, the working fluid in the energy collector is vaporized and communicated into a containment assembly at 912, where the vaporized working fluid exerts pressure on a storage fluid in the containment assembly to transport the storage fluid to a high potential reservoir. At 912, the vaporized working fluid from the containment assembly is communicated to a condenser where it is condensed. At 914, the expansion medium from the condenser is communicated to the expansion medium reservoir. Operation 916 is next and includes supplying the storage fluid from the high potential reservoir to a generator where energy is generated. At 918, the storage fluid from the generator is communicated to a low potential reservoir, and at 920 is communicated to the containment assembly. The method ends at 922.

[0069] FIG. 10 illustrates a method of generating electricity, in accordance with the invention. The method begins at 1002. At 1006, working fluid stored in a reservoir is transported using gravity to a solar collector where it is vaporized by solar energy. At 1008, the vaporized working fluid is communicated into a containment assembly, where the vaporized working fluid exerts pressure on a storage fluid in the containment assembly which transports the storage fluid to a high potential reservoir. At 1010, the vaporized working fluid is communicated from the containment assembly to a condenser where it is condensed by heat transfer to the ambient environment. Operation 1012 is next and includes using gravity to transport the working fluid from the condenser to the working fluid reservoir. At 1014, the storage fluid supplied from the high potential reservoir to an electrical generator, whereby electricity is generated. At 1016, the storage fluid is exhausted from the electrical generator to a low potential reservoir, and transported using gravity to the containment assembly at 1016. The method ends at 1020.

[0070] FIG. 11 is diagrammatic view of an embodiment of an energy generation system 100 corresponding to that shown in FIGs 4-6. A reservoir 126 holds an expansion medium, i.e., a working fluid, 127 and may be connected by a pipe 166 to a collector 120. A valve 146 may control the flow of expansion medium 127 between reservoir 126 and collector 120. Flow of expansion medium 127 from reservoir 126 to collector 120 may be induced by gravity or pumping. Collector 120 is configured to increase the temperature of the expansion medium flowing through it when exposed a source of energy, such as the sun. Once the temperature of the expansion medium 127 in collector 120 reaches a critical temperature, it undergoes a phase change from a liquid to a vapor. The gaseous expansion medium vapor 128 occupies a larger volume than the liquid expansion medium 127, and it may be communicated through pipe 164 into a displacement chamber 122 contained in the interior 116 of a containment assembly 130. A valve 144 may control the communication of vapor 128 from collector 120 to displacement chamber 122. Significantly, the displacement chamber 122 may be constructed, as with bellows or the like, to increase its volume in response to increasing pressure within the displacement chamber so as to maintain the pressure in the chamber substantially constant. Accordingly, as the vapor 128 expands into displacement chamber 122, the displacement chamber 122 increases in volume. Pressure exerted by liquid working fluid in chamber 116 on the vapor in expandable displacement chamber 122 causes the vapor to flow through a pressure equalization line 168 to maintain approximately equal pressure between collector 120 and reservoir 126. A valve 148 may control the communication between reservoir 126 and collector 120.

[0071] When displacement chamber 122 has increased by a predetermined volume, ΔV1 , expansion medium vapor 128 may be conducted through a pipe 165 to a condenser 124. A valve 146 may control flow of the vapor 128 between the displacement chamber and the condenser. In condenser 124, the expansion medium vapor 128 undergoes a phase change from a vapor 128 to a liquid 127. In undergoing this phase change from vapor to liquid-, the expansion medium vapor 128 decreases by a predetermined volume ΔV2 in the condenser, and displacement chamber 122 also decreases by about the same predetermined volume ΔV2. The expansion liquid 127 may flow to reservoir 126 through a pipe 167 between condenser 124 and reservoir 126 may be controlled by a valve 147. The flow of condensed expansion liquid 127 from condenser 124 to reservoir 126 may be induced by gravity or pumping.

[0072] Containment assembly 130 also contains a storage medium, e.g., a fluid, 129 in the containment assembly interior 116. As displacement chamber 122 expands inside of containment assembly interior 116, pressure on storage medium 129 causes it to be displaced and communicated by a pipe 163 to a high potential energy reservoir 110. A valve 143 may control the communication of storage medium 129 between the containment assembly interior 1 16 and the reservoir 110. Subsequently, the storage medium 129 may then be communicated from the high potential energy reservoir 110 through a pipe 169 to a prime mover 112, such as a generator, a turbine, or other power producing device. A valve 149 may control the communication of storage medium between the high potential reservoir 110 and prime mover 112. Storage medium 129 may then be communicated through a pipe 161 from the prime mover to a low potential reservoir 114. A valve 141 may control the communication of the storage medium between the prime mover and the low potential reservoir. Storage medium 129 may then be communicated through a pipe 162 from the low potential reservoir 114 to the interior 116 of containment assembly 130, A valve 142 may control this flow.

[0073] As discussed above, the flow of expansion medium 127 from reservoir 126 to collector 120 may be induced by gravity or pumping. Placing the reservoir 126 at a higher gravitational potential than the collector 120, i.e., at a higher height than the collector, enables the expansion medium 127 to flow down under the influence of gravity from the reservoir 126 to the collector 120. Pressure equalization line 168 prevents a vacuum from disrupting the flow of expansion medium between reservoir 126 and collector 120 by equalizing the pressure between reservoir 126 and collector 120.

[0074] High potential reservoir 110 is preferably placed at an elevation or height H1 above the containment assembly 130 so that the work required to move the storage medium 129 from containment assembly 130 to the high potential reservoir 110 is imparted to the storage medium as potential energy. At such elevation H1 , the storage medium in the high potential reservoir exerts a pressure P1 through pipe 163 at containment assembly 130. The pressure P1 is determined by the height H1 of high potential reservoir 110 above containment assembly 130. For example, when the storage medium 129 is water, the pressure P1 is about 0.43 pounds per square inch for each foot of height H1. For a height H1 of about 1300 feet, the pressure at the containment assembly 130 will be about 560 pounds per square inch (560 psi).

[0075] The minimum amount of work, W, required to raise a predetermined mass M1 of storage medium 129 from the containment assembly 130 to the high potential reservoir 110 is simply the mass M1 , times the height H1, times gravitational acceleration g, or:

W = M1^*g^*H1 (1)

[0076] The storage media 129 in high potential reservoir has a potential energy equal to the work W. This potential energy is available for conversion to some other form of energy, for example electricity. For example, a portion of this potential energy may be used to operate the prime mover 112. The prime mover 112 may be placed a distance H2 below the high potential reservoir 110, so that the amount of potential energy E available to operate generator 112 may be calculated as the predetermined mass M2 of the storage medium released to the prime mover 112, times the distance H2, times g or:

E = M2*g*H2 (2)

[0077] While a generator is an example of a prime mover that may be used, other forms of energy conversion apparatus may also be utilized to advantage. For example, mechanical energy may be extracted from the potential energy E in a variety of ways well known in the mechanical and hydraulic arts.

[0078] Moreover, storage medium 129 could also be used to raise a mass other than the storage medium 129 to the high potential reservoir 110. For example the storage medium could be employed to provide power other types of mechanical and hydraulic apparatus adapted to lifting a discrete object, or solid mass (such as rock or grain, for example) to the high potential reservoir [0079] As indicated above, the temperature of expansion medium 127 rises in collector 120 until the critical temperature of the expansion medium is reached. The critical temperature of a fluid is the temperature at which the fluid will undergo a phase change from fluid to vapor at the ambient pressure. For example, the critical temperature of a common refrigerant R-410A is about 150 degrees F at an ambient pressure of 550 - 600 psi. The ambient pressure in the interior 116 of containment assembly 130 may be the pressure P1 , as determined by the elevation H1 of the high potential reservoir 110 above the containment assembly 130. As indicated, when elevation H1 is about 1300 feet the pressure P1 at the containment assembly interior will be about 560 psi and the R-41 OA would undergo a phase change from fluid to vapor at about 150 degrees F. At the critical temperature, additional heat energy (for example heat energy from solar energy) applied to the collector 120, causes additional molecules of the expansion medium to undergo the transition from fluid to vapor without increasing the temperature of the expansion medium above the critical temperature. R-41 OA is given by way of example as a suitable expansion medium, but many other types of expansion media may be used, as previously described.

[0080] As discussed above, when displacement chamber 122 has expanded to a predetermined volume, the expansion medium vapor 128 in displacement chamber 122 may be conducted through a pipe 165 to a condenser 124. Condenser 124 may be maintained at a temperature substantially below the temperature of the collector 120 during the expansion of the expansion medium fluid into a vapor. At a lower temperature, the expansion medium will condense at a substantially lower pressure. Storage medium 129 in low potential reservoir 114 may be used to displace expansion medium vapor 128 from displacement chamber 122 through pipe 165 into condenser 124. A pressure P2 may be exerted through pipe 162 to compress displacement chamber 122 and exert a pressure P2 on the expansion vapor therein. The pressure P2 may be determined by the elevation H3 of the low potential reservoir 114 above the containment assembly 130. For example, when elevation H3 is about 230 feet, pressure P2 may be about 100 psi. At about 90 - 120 psi, R-410A_.vapor will condense at about 50 degrees F, for example.

[0081] The available work, Wa, from energy system 100 is the change in volume ΔV1 times the pressure P1 minus the change in volume ΔV2 times the pressure P2 or:

Wa = P1* ΔV1 - P2*ΔV2 (3)

When ΔV1 = ΔV2, the available work is:

Wa = ΔV1 (P1 - P2) (4)

[0082] As discussed above, the flow of expansion medium 127 from condenser 124 to reservoir 126 may be induced by gravity or pumping means. Placing the condenser 124 at a higher gravitational potential than reservoir 126, that is above the reservoir 126, enables the expansion medium 127 to flow down under the influence of gravity from the condenser to the reservoir 126.

[0083] In an example of operation of the energy generator system 100, solar energy may be used during the day to cause expansion of an expansion fluid 127 to an expansion vapor 128. The expansion vapor may be used in the containment assembly 130 to pump water during a pumping step up to high potential reservoir 110, for example a lake at a high level. The water may then generate electricity by running back down through a turbine during an energy generation step to low potential reservoir 114, for example to a lake at a lower level. At night, when the condenser 124 has been cooled by giving off energy in the form of radiation to the sky, water in the low potential reservoir 114 may then be used to recόmpress the expansion vapor 128 into an expansion fluid 127 in the condenser 124. In this case, energy may be input into the system 100 during the daytime from a high energy source, e.g., solar radiation. Energy may be output from the system 100 during the nighttime into a low energy sink, as by radiation to a black body (e.g., into space). The energy source is the sun, and the energy sink is space. The energy generator system 100 extracts useful work or electricity by moderating the flow of energy from the high-energy source to the low energy source. [0084] Table 1 below illustrates examples of valve states for the system 100 of FIG. 11 during a pumping phase, an energy generation phase and a recompression phase (either warm or cold). During conversion of heat energy to potential energy (the pumping phase), valves 142, 145, and 147 may be closed while valves 143, 144, 146, and 148 may be open. During the day, solar energy heats the collector 120 and the expansion medium 127, for example R-410, expands to an expansion vapor at about 150 degrees F at a pressure of about 550 - 600 psi. Expanded vapor 128 flows through pipe 164 and open valve 144 into displacement chamber 122. Valve 145 may be closed, thus forcing displacement chamber 122 to expand inside containment assembly 130. As expansion medium 127 is used up by expansion into vapor 128, the expansion medium 127 may be replaced from reservoir 126 through pipe 166 by opening valve 146. Placing reservoir 126 above collector 120 enables gravitational flow of expansion medium 127 downhill from reservoir 126 to collector 120 through valve 146. Valve 148 permits pressure equalization through pipe 168 between collector 120 and reservoir 126, thus enabling flow from reservoir 126 to collector 120. Expansion of the displacement chamber 122. displaces the storage medium 129, for example water. The water is forced up hill to the high potential reservoir 110 through pipe 163 and valve 143 by the expansion of the working fluid to vapor. Valves 143 and 146 may be partially opened to control pressures in the containment assembly 130, and may be adjusted to optimize the work extracted in lifting water to the high elevation lake 110. Once in the lake (high potential reservoir 110), the water may be released through valves 141 , 149, as desired, to generate electricity. Thus the generation step may be independent of, or coincident with, either the pumping step or the recompression step. Valves 141 and 149 may be opened or closed as the generator may or may not be operated during the pumping step. The following Table 1 illustrates the valve states during different phases of operation of system 100. Expansion medium/vapor Storage Media valves --> 144 145 14£ > 147 148 141 142143149 state

Pumping step 1 0 1 0 1 X 0 1 X

Energy generation step X X X X X 1 X X 1

Recompression step (warm) 0 1 0 1 0 X 1 0 X

Recompression step (cold) 0 1 X 1 X X 1 0 X

state: 1 = open; 0 = closed; X = open or closed

Table 1

[0085] During the energy generation phase, as illustrated in Table 1 the expansion medium, water for example, may be released through pipe 169 by opening valve 149 and valve 141. Valve 149 may be redundant but it is desirable because it permits retaining the water in the lake with minimal pressure head on the generator 112. Valves 142, 143, 144, 145, 146, 147, and 148 may be open or closed during the energy generation step. The water may flow through generator 112, for example, a turbine, to generate electricity. Alternatively, the water may be used to perform other forms of work. Open valve 141 permits water to flow through pipe 161 to low potential reservoir 114, for example, a low level lake. The water may be stored in the low potential reservoir until time for recompression of the expansion medium vapor 128 back into the expansion medium 127 during the recompression step.

[0086] During the recompression phase, as illustrated in Table 1 , valves 142, 145, and 147 may be open, and valves 143 and 144 may be closed. Valves 141 and 149 may be either open or closed. Valves 146 and 148 may be open or closed when the recompression step is performed under cold conditions, that is when the temperature of collector 120 is about the temperature of the condenser 124 or lower. When recompression is done under warm conditions, that is when the temperature of collector 120 is above the temperature of condenser 124, then valve 146 and 148 are preferably closed. Recompression may take place when the condenser 124 reaches a substantially lower temperature than the pumping phase temperature, for example, about 50 degrees F. At about 50 degrees F R-410A may be recompressed at a pressure of about 90 - 120 psi. A pressure of about 90 - 120 psi may be exerted by a pressure head of about 200 feet. Therefore, the low level reservoir may be located about 200 feet above the containment assembly 130. The recompression takes place as water from the low potential reservoir 114 flows down to the containment assembly 130 through pipe 162 and valve 142. The water urges the expansion medium vapor 128 through pipe 165 and valve 145 to the condenser 124. The condenser is preferably maintained at about 50 degrees F. In the condenser the expansion medium vapor 128 condenses to the expansion medium fluid 127. Condensation of the expansion medium vapor 127 to the expansion medium fluid 128 creates a low-pressure region in the condenser 124 that draws more expansion medium vapor 128 into condenser 124 for condensation. Heat energy is released by the condensation process.

[0087] The condenser 124 may dissipate this heat energy through a number of methods. For example, the recompression may be conducted at night when the ambient temperatures are substantially lower than during the daylight hours. Such substantially lower temperature may be sustained by radiation from the condenser into a black body, such as a clear night sky, i.e., into space. The condenser may also be placed in a body of water, such as a lake, for example. Such bodies of water may be sized to afford a good sink and accept large quantities of heat energy from the condenser 124, thus advantageously maintaining the condenser 124 at a substantially constant temperature. Moreover, bodies of water make excellent radiators into the clear night sky. In accepting heat energy from the condenser 124 and radiating it into a black body, such as space, bodies of water act as heat conductors to conduct heat from the condenser 124 to space. An example of a large body of water or lake may be the low potential reservoir 114.

[0088] FIG. 12 is diagrammatic view of one embodiment of a solar pumping system 200. The system of FIG. 12 may be substantially similar to the system 100 of FIG. 11 , except that instead of using a storage medium or fluid 129, the system may be used to communicate a working pump fluid 229, e.g., water, from a low position reservoir 214 to a high position reservoir 210, where the pump fluid may be stored or use, e.g., for irrigation, and the system 200 does not have a return path through a prime mover 112 (and the associated components) for energy generation as does the system 100 of FIG. 11.

[0089] The operation of the system 200 of FIG. 12 may be substantially the same as that described above for the system 100 of FIG. 11. As with system 100, the pump fluid 229 may also provide power to a mechanical and hydraulic apparatus, for example, to lift a discrete object or a solid mass (such as rock or grain, for example) to the location of high position reservoir 210.

[0090] Low position reservoir 214 may be any source of pump fluid 229 which it is desired to pump to a higher location. Preferably, since pump fluid is not returned to low position reservoir 214, the low position reservoir 214 may be a source of pump fluid that is functionally unlimited, such as a lake, an aqueduct, or a river.

[0091] The valve states during operation of the system 200 may be the same as shown in Table 1 , except that there are no valves 141 and 149 in system 200 since there is no return path from the high position reservoir.

[0092] FIG. 13 is a diagrammatic view of a first embodiment of a containment assembly 130 that may be employed in systems in accordance with the invention. FIG. 13 illustrates the expansion medium vapor 128 in the displacement chamber 122 separated from the storage medium 129 by a piston 310. Piston 310 may be a mechanical piston, as is well known in the mechanical arts, or a layer of fluid adapted to form a barrier between storage medium 129 and expansion medium vapor 128, the fluid being non-miscible with the storage medium 129 and the expansion medium vapor 128. A suitable fluid layer piston, where the storage medium 129 is water, is an oil that is non-miscible with water.

[0093] As illustrated in Table 1 above, during the pumping step of the cycle, valves 143 and 144 are open while 142 and 145 are closed. Expansion medium vapor 128 may be admitted to the interior 122 of the displacement chamber at a higher pressure than the pressure on the storage medium 129, and the storage medium is displaced and exits through pipe 163 and valve 143. During the recompression step, valves 143 and 144 may be closed while valves 142 and 145 may be open to control flow through pipes 162, 163, 164, and 165. Pressure from the low potential reservoir 114 drives piston 310 against the expansion medium vapor 127 in displacement chamber 122. Displacement chamber 122 decreases in volume, and the expansion medium vapor 128 exits the displacement chamber through pipe 165 and valve 145. As described above, the movable piston and the operation of the containment assembly advantageously insures that the expansion and recompression of the expansion medium is accomplished at substantially constant pressure.

[0094] FIG. 14 is a diagrammatic view of another embodiment of a containment assembly 130 that may be used in the invention. FIG. 14 illustrates the expansion medium vapor 128 in the displacement chamber 122 which is separated from the storage medium 129 by a moveable piston 310. As with FIG. 13, piston 310 may be a mechanical piston or a layer of non- miscible fluid adapted to form a barrier between storage medium and the expansion medium vapor. The piston 310 separates the expansion medium vapor 128 from the storage media 129 and preventing mixing of the fluid 129 with the vapor 128. When piston 310 is a layer of fluid, such as oil, the piston has the added advantage of being capable of sealing complex or irregular interior surfaces of the containment assembly.

[0095] Tube 170 may communicate the storage medium 129 from the containment chamber 130 through a single orifice in the containment chamber wall to valves 142 and 143, thus preserving the structural integrity of containment chamber 130. Similarly, tube 171 may communicate the expansion medium vapor 128 to the containment assembly through pipes 164 and 165 controlled by valves 144 and 145, respectively.

Pixelization of Energy Collection for Energy Concentration .

[0096] Conventional thermal energy conversion systems typically concentrate the thermal energy in one location so that one central converter can transform the thermal energy into another useful form of energy such as electricity. The invention advantageously enables a different approach, referred to herein as "pixelization", whereby multiple dispersed energy conversion systems (or portions thereof) such as previously described may be combined into a single system that effectively sums the individual contribution of each individual system. Pixelization in accordance with the invention may accomplished by moving storage media (e.g., water, or another storage media) from point to point rather than by moving the thermal energy to a central site. This movement of the storage medium from many dispersed collectors to a central collection site, for example, allows for the collected energy to be concentrated by adding the output of multiple fluid pumps of lower capacity, and reduces the need to transport heat over large distances to a central evaporator. Multiple evaporators can be positioned close to the solar collectors. Also, pixelization allows for the full displacement of a given chamber's working medium by hot gaseous expansion of the medium, and the use of the hot gaseous expansion to preheat liquid expansion medium that will be boiled off (converted to vapor, as described above) to evacuate other chambers of their working medium. Using several chambers in sequence will allow almost all of the heat energy that was used to raise expansion medium in a first chamber to the boiling point to be captured and reused, thus increasing system efficiency substantially. Also, because the chambers that have been used for heat exchange have a lower pressure, they can be partially refilled with working medium and reheated to drive even more working medium to a higher potential energy point.

[0097] FIG. 15A is a block diagram of a system for the pixelized collection of energy, in accordance with the invention. A plurality of energy generator assemblies 100' a-n may move a storage medium through a manifold 510 to a high potential energy reservoir 110. Moreover, the transformation of thermal energy to another form of energy can be performed by multiple units at dispersed localized locations, and the transformed energy (e.g., the movement of a storage medium, such as water, to a higher elevation) from the dispersed units may be transported and added together at one or more other locations to take advantage of economies of scale in the transformation of potential energy into electrical energy, or in pumping or refrigeration applications.

[0098] A principal advantage with this system is that the losses associated with the transportation of low heat differential masses are minimized, and the savings are transformed into the increase in potential energy of the storage medium. Individual pixelization units can also be run using standard Rankine cycle pumps. Moreover, standard Rankine cycle pumps can be used in a first group of pixelization units, and modified Rankine cycle pumps of the invention, such as shown in FIG. 2, can be used in a second group of pixelization units and their energy contributions combined.

[0099] FIG. 15B is a diagrammatic view of an embodiment of a pixelized energy generation system in accordance with the invention that comprises a plurality of two or more interconnected energy generator assemblies 100'a-n that have a common manifold 510 for receiving and combining the pump storage media from the individual generator assemblies 100'a-n. The energy generator assemblies 100'a-n may be placed in dispersed locations or collocated in an array. Each of the energy generator assemblies 100'a-n produces a partial contribution to the total combined energy from the group of generator assemblies which is combined at the manifold 510 with the partial contributions from other generator assemblies. The partial energy generated by each of the energy generator assemblies 100'a-n may be proportional to the area of sunlight striking the energy generator assembly. The manifold 510 may communicate the combined energy to a high potential reservoir 110 through a pipe 163, where the contribution of each energy generator assembly 100'a-n may be accumulated.

[00100] FIG. 15C is a diagrammatic illustration of an alternative embodiment of an energy generation system similar to that shown in FIG. 15B, except that instead of a common manifold, the partial contributions of the individual energy generator assemblies 100'a-n are separately communicated to the high position reservoir 110 by separate lines 163a-n, each controlled by a corresponding valve 143a-n. The system of FIG. 15C is more appropriate where the various energy generator assemblies 100'a-n are dispersed to different locations, and it is more efficient to separately provide storage media for the individual assemblies to the reservoir than to combine the storage media in a common manifold as in FIG. 15B

[00101] As discussed above, in both of the embodiments of FIGs. 15B and C, storage media 129 may released through a generator 112 to flow to a low potential reservoir 114, and the storage media from the low potential reservoir 114 through pipe 162 and distributed through manifold 514 through valves 142a-n to energy assemblies 100'a-n. Thus, energy generator assemblies 100'a-n may advantageously be a large number of small generator systems distributed over a large area, and may be built on a small-scale with the economy of large-scale generators and reservoirs. This permits concentration of partial energy from many small energy generator assemblies 100' composed of modest part sizes optimized to exploit economies of mass production, and that may not even be in line of sight of each other. For example, energy generator assemblies 100'a-n that are separated by buildings or terrain such as terrain including one or more hills or bluffs may still contribute energy to the system through plumbing connected to the reservoir 110. Thus, energy generator assemblies 100'a-n are capable functioning in terrain where mirror systems for concentrating solar energy might be impractical because the line of sight is blocked. Moreover, energy generator assemblies 100'a-n that are spread over a large or irregular area, beyond the practical range of a lens concentrating system, may still contribute substantial energy to the system through plumbing connected to the reservoir 110.

[00102] FIG. 16 is a flowchart of a method of converting thermal energy to another useful form of energy, in the systems of FIGs. 15 A-C. The method begins at 1602. At1604, thermal energy may be absorbed into an expansion medium at a plurality of energy generator assemblies. At 1606, at least a portion of the Expansion medium may be vaporized to exert pressure on a storage medium to displace at least a portion of the storage medium at the plurality of energy generator assemblies. Operation 1608 is next and includes condensing substantially the portion of the expansion medium that was vaporized. At 1610, the displaced portion of the storage media from the plurality of energy generator assemblies may be collected. At 1612, the displaced portion of the storage medium displaced to a higher potential energy state is supplied to power at least one turbine to produce a second form of energy. At 1614, substantially the portion of storage media from the at least one turbine is supplied to a lower potential energy state. The method ends in operation 1616.

[00104] FIG. 17 is a diagrammatic view of a fractal solar energy- collector array that may be used in the above systems for the pixelized collection of energy. The fractal solar energy collector 1710 may comprise arrays of a plurality of solar energy collectors 1702, arranged in a fractal pattern of, for example, sixteen collector groups 1704, arranged in a fractal pattern of, for example, sixty-four collector groups 1706, all connected to a fractal expansion medium transport system 1708.

[00105] A fractal solar energy collector array as shown in FIG. 17 may be advantageously dispersed across a landscape for the pixelized collection of energy, and connected to natural or man-made reservoirs or lakes for the storage and release of storage medium through one or more generators, or in the case of pumping systems, for the transport of water, for example, through aqueducts or the like.

Refrigeration and Generation of Cryogenic Fluids

[00106] As described in the foregoing, the invention may use a prime mover such as turbine or a generator to transform thermal energy to a second form of energy. The turbine may comprise a compressor in a refrigeration or air conditioning system, thus affording solar refrigeration and air conditioning systems, or may be used as part of a multiple stage refrigeration system to generate cryogenic fluids (e.g., liquid nitrogen, liquid air, liquid oxygen, etc.). The compressor can be a conventional closed-loop heat pump arrangement to compress a gas which is allowed to expand at another location and absorb thermal energy for the expansion to cool an object (e.g., the inside of a refrigerator, or an equivalent space). Cryogenic temperatures can be reached by a multiple stage implementation of heat pumps, and the cryogenic fluids (e.g., liquid nitrogen, liquid oxygen, etc.) may be used locally or transported to other locations for use in any of a variety of different applications (e.g., transportation, energy generation, various chemical processes, or equivalents).

[00107] As will be appreciated, while the invention has been described with reference to preferred embodiments, various changes in these embodiments may be made without departing from the spirit and principles of the invention, the scope of which is defined in the appended claims.

Claims

1. A method of converting thermal energy, comprising: supplying thermal energy to a working medium to cause expansion of at least a portion of the working medium at substantially constant pressure; imparting energy to a storage medium using said expansion of the working medium to change the energy state of the storage medium from a low potential energy to a higher potential energy; and removing thermal energy from the working medium to return said working medium to a non-expanded state while maintaining said substantially constant pressure.

2. The method of Claim 1 , wherein said supplying comprises supplying solar energy to said working medium, and said removing comprising transferring heat from said working medium to an energy sink.

3. The method of Claim 2, wherein said supplying comprises passing said working medium through a solar collector during daylight hours, and said removing comprises cooling the working medium in a condenser during nighttime hours.

4. The method of Claim 1 , wherein said working medium comprises a working fluid, and said supplying comprises expanding said working fluid to a gas in a container having a changing volume so as to maintain the gas at said substantially constant pressure.

5. The method of Claim 4, w,herein said supplying comprises supplying additional thermal energy to the gas to increase the enthalpy of the gas.

6. The method of Claim 4, wherein said removing thermal energy from said working medium comprises using said removed thermal energy to preheat another working medium in another changing volume container of a pixelated system to promote expansion of said other working medium.

7. The method of Claim 4, wherein said working fluid is selected from the group consisting of acetone, alcohol, water, various water solutions, ammonia and water solutions, carbon dioxide, liquefied natural gas (LNG), chloro- fluorocarbon (CFC) refrigerants R-410A, R-22, R-32, R-125, R-407C, R-134A, and HCFC refrigerants.

8. The method of Claim 4, wherein said removing thermal energy comprises cooling the expanded working fluid while reducing the volume of said container so as to maintain said substantially constant pressure within said container.

9. The method of Claim 4, wherein said imparting energy to said storage medium comprises applying energy to said storage medium using the changing volume of said container.

10. The method of Claim 1 , wherein said converting comprising supplying at least a portion of the higher potential energy storage medium to a prime mover at a lower potential energy level to convert said higher potential energy to another form of energy using said prime mover.

11. The method of Claim 10, wherein said prime mover comprises a generator, and said other form of energy comprises electricity.

12. The method of Claim 10, wherein said prime mover comprises a compressor in a refrigeration system, and said other form of energy is used to produce a cryogenic fluid.

13. The method of Claim 1 , wherein said imparting energy to said storage medium comprises displacing said storage medium to an elevated height.

14. The method of Claim 13, wherein said storage medium comprises a fluid, and said displacing comprises pumping said fluid to a reservoir at said elevated height.

15. A method of converting thermal energy to another form, comprising: supplying thermal energy to a working fluid in a plurality of container assemblies having changeable volumes so as to cause expansion to a gas at a substantially constant pressure of at least a portion of said working fluid in some of said plurality of container assemblies; removing thermal energy from the gas in one or more of said container assemblies to condense said gas back to said working fluid while maintaining said substantially constant pressure; supplying a portion of said removed thermal energy to working fluid in other ones of said container assemblies to preheat the working fluid in said other ones of said container assemblies to promote expansion of the working fluid therein to a gas; and imparting energy to a storage medium using said expansion of working fluid to a gas to change the energy state of said storage medium to a high energy level.

16. The method of Claim 15, wherein said supplying thermal energy comprises supplying solar energy from a plurality of solar collectors, at least one solar collector being associated with one or more of said container assemblies; and said removing thermal energy from said gas comprises condensing said gas back to said working fluid using a plurality of condensers, at least one condenser being associated with one or more of said container assemblies.

17. The method of Claim 16, wherein said pluralities of solar collectors, container assemblies and condensers are dispersed over a landscape, and wherein said imparting energy to said storage medium comprises transporting said storage medium to a storage reservoir at an elevated level above said pluralities of solar collectors, container assemblies and condensers.

18. The method of Claim 17 further comprising supplying at least a portion of said storage medium from said reservoir to a prime mover at a lower level to convert a portion of the high energy of said storage medium to another form of energy from the prime mover.

19. The method of Claim 18 further comprising returning storage medium from said low level to said container assemblies to maintain said substantially constant pressure on said working fluid.

20. The method of Claim 16, wherein said supplying solar energy comprises supplying heat to the working fluid during daylight hours, and said removing of thermal energy comprises condensing said gas during nighttime hours.

21. The method of Claim 15, wherein said storage medium is selected from the group comprising fluids, slurries, and solid masses.

22. Apparatus for converting thermal energy, comprising: a solar collector for supplying solar energy to an expansion medium circulating therethrough; a containment assembly having first and second chambers with changeable volumes, said solar energy causing expansion to a gas at substantially constant pressure of said expansion medium from said solar collector within the first chamber, the second chamber of said containment assembly containing a storage medium, and said changing volumes imparting energy to the storage medium to move the storage medium to a high potential energy reservoir; a condenser for removing heat energy from said gas from said first chamber, while maintaining said substantially constant pressure, to convert the gas back to said expansion medium; and a prime mover for converting energy from said storage medium in said high potential energy reservoir to another form upon said storage medium moving to a low potential energy reservoir.

23. The apparatus of Claim 22, wherein said containment assembly comprises a container having a moveable separator therein dividing the container into said first and second chambers, the volumes of said chambers changing in relation to the movement of said moveable separator.

24. The apparatus of Claim 23, wherein said expansion medium and said storage medium respectively comprise an expansion fluid and a storage fluid, and said moveable separator comprises a layer of non-miscible fluid that moves in response to pressure changes between the first and second chambers to change the volumes of said chambers.

25. The apparatus of Claim 24, wherein the expansion of said expansion fluid to said gas in the first chamber increases the volume of the first chamber and decreases the volume of the second chamber and exert pressure on said storage fluid in the second chamber to displace said storage fluid to said high potential energy reservoir.

26. The apparatus of Claim 23, wherein said solar collector comprises a fractal array of a plurality of solar collector units arranged in collector groups, and a transport system connecting said plurality of solar collector units for conveying expansion medium through said units.

27. The apparatus of Claim 26, wherein there are pluralities of containment assemblies and condensers connected to said fractal array of solar collector units to form a pixelized energy conversion system, one or more of said containment assemblies, condensers and collector units being associated together to form corresponding pluralities of energy generator assemblies of said system.

28. The apparatus of Claim 22, wherein said energy conversion units of said system are dispersed across a landscape, and said high potential energy and said low potential energy reservoirs comprise lakes.